712 J. H. GARDNER TflE MID-CONTINENT OIL FIELDS 



by Muiiii ill the Grandfield district of southern Oklahoma (Bulletin 547, 

 United States Geological Surve_y)- But the Angelina-Caldwell niono- 

 clinal flexure lies in a northeast-southwest direction roughly parallel to 

 the Gulf coast and is possibly related to parallel fault zones in connection 

 with the saline domes of the coast oil fields. 



Thus it appears evident that the two lines of structure are the results 

 of different orogenic movements. The Sabine uplift lies between the two 

 convergent lines of disturbance and has its present structural form as a 

 result of stresses acting on it at more than one geological period. Cer- 

 tainly one of the principal movements was in the later Tertiary. Veatch 

 calls attention to the fact that more recent displacements along the fault 

 have involved the Pleistocene deposits adjacent to the Ouachita River 

 just above Alabama Landing. These recent movements far to the north 

 suggest that the stresses that initiated tlie uplifts in the form of saline 

 domes and faults along the coast were expressions of a compression that 

 was of a regional nature. 



Local structures, such as those that characterize the oil fields in the 

 Caddo and Crichton districts, are not of the saline dome type, but are 

 small folds due to crumpling of the strata on the larger ujilift (see figure 

 8). Matson calls attention to the fact that the local anticlines at Caddo 

 show cross-folding, and that the axes which lie northeast and southwest 

 are older than those which cross them from northwest to southeast. It is 

 interesting to note that these two lines of folding lie roughly parallel with 

 the two major lines of structural movement above mentioned, and that 

 the more recent of these small folds are parallel with the recent fault- 

 ing in the northwest-southeast direction along the fault near Alabama 

 Landing. 



'to* 



Origin of the Petroleum and Natural Gas 



It seems practically inevitable to the writer that any geologist who 

 comes to be familiar with the occurrence of oil and gas in the Mid-Con- 

 tinent field must sooner or later take the view that these substances have 

 originated from strata of hydro-carbon bearing shale; such deposits lie 

 within or inter-stratified with the sandstone beds or other porous rocks 

 that contain the accumulated deposits. We are practically forced to this 

 theory of oil origin by a process of exclusion. With the present limited 

 store of facts regarding the original source of petroleum and its associated 

 gases, it is scarcely possible to select any theory other than the above 

 mentioned without having arrayed against it a mass of facts with which 

 it is entirely inconsistent. Marius P. Campbell has stated in his his.- 



